ultra low speeds with 3.17-rc1 and rc2 kernels
https://bugzilla.kernel.org/show_bug.cgi?id=83271
190 KB/s max read speed vs over 12 meg/sec with 3.16 kernel

reverting this commit fixes this:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6a38fa0e3c94dfd1394a71a2d47c9c4d47367374

git revert -n 6a38fa0e3c94dfd1394a71a2d47c9c4d47367374

